Lobster Mac and Cheese

1 . Stage

Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in boiling water, stirring occasionally, until tender yet firm to the bite, about 8 minutes. Reserve 2 cups hot pasta water, then drain macaroni in a colander set in the sink. Rinse with cold water to cool; set aside.

2 . Stage

Pour reserved pasta water into the same pot and add lobster halves, cut-side up. Bring to a boil, then reduce heat to medium-low, cover, and steam until lobster meat firms and turns opaque, about 3 minutes. Remove lobster to a tray and cool for a few minutes, then remove meat and cut into bite-sized pieces. Reserve shells.

3 . Stage

Melt 2 tablespoons butter in a saucepan over medium heat. Cook and stir onion in hot butter until onion is softened and translucent, about 5 minutes. Remove onions to a small bowl; set aside. Place reserved lobster shells, milk, shallot, peppercorns, and garlic into the same saucepan. Bring to a gentle simmer over medium heat and cook for 20 minutes.

4 . Stage

Preheat the oven to 350 degrees F (175 degrees C).

5 . Stage

Melt remaining 5 tablespoons butter in a separate saucepan over medium-low heat. Whisk in flour and stir until mixture turns pasty and light golden brown, about 10 minutes. Strain milk mixture through a mesh sieve and slowly pour into flour mixture while whisking. Bring to a simmer over medium heat; cook and stir until thick and smooth, 10 to 15 minutes. Remove from heat.

6 . Stage

Stir Gruyère, Cheddar, and Romano cheeses into thickened milk mixture until melted and smooth. Season with salt and pepper, then stir in reserved lobster meat, onions, and macaroni. Pour mixture into a 4-quart casserole dish and smooth the top. Sprinkle evenly with panko crumbs.

7 . Stage

Bake in the preheated oven until sauce is bubbly and the top is golden brown, 8 to 12 minutes.